The timing of the announcement of the fresh probe could not be worse for the Culture Secretary, who is due to appear in front of the Leveson inquiry into press ethics towards the end of next week, most likely on Thursday.

Sir John Lyon, Parliamentary standards commissioner, initiated the probe in response to a complaint earlier this month from Labour MP Stephen McCabe.

Mr McCabe wrote to the commissioner raising concerns about a series of “networking events” involving eight creative industry organisations which culture minister Ed Vaizey said he and Mr Hunt had attended while in opposition.

Mr Vaizey recorded the events in the register of interests as donations in kind worth a total of around £27,000. Mr Hunt was at some of the meetings but did not mention them in his own entry in the register.

Mr Hunt has since accepted that he attended three of the meetings, worth a total of £7,471, and has amended his register of members’ interests accordingly.

Sir John’s office in the Houses of Parliament confirmed he said that he had “accepted [the complaint] for inquiry”, but declined to comment further.

Any probe by Sir John can take between three months and a year. Last year fewer than half of Sir John’s 33 investigations were completed within nine months, but all but one were completeted within 12 months.

if Sir John finds Mr Hunt broke the rules, a committee of MPs has to decide on any sanction. Punishments can include being forced to apologise to MPs in the House of Commons.

A spokesman for Mr Hunt said: “As soon as we realised there was a mistake we amended the register. We will cooperate fully with any lines of inquiry.”

Mr Hunt is preparing for his make-or-break appearance in front of the Leveson inquiry next week, most probably on Thursday 31 May.

His responses to questioning from the inquiry’s lawyers will determine whether he survives as Culture Secretary or is sacked, immediately or at the next Cabinet reshuffle, which is expected in September.

Mr Hunt will come under particular scrutiny over whether he acted improperly in the handling of a multi-billion pound bid for all of the shares in BSkyB, the satellite broadcasting company controlled by Rupert Murdoch’s News Corporation.

He is facing demands to resign after it emerged that his former special adviser, Adam Smith, had engaged in extended contact with News Corp at a time when Mr Hunt was responsible for adjudicating on the company’s bid for full control of BSkyB.